Angle that is smaller than a right angle (less than 90Â°). Angle formed by two lines or two perpendicular planes that measures 90Â°. Symbol denoting that a straight line meets another at a right angle. Symbol denoting that two straight lines do not remain at a constant distance from one other. Symbol denoting that two straight lines remain at a constant distance from one another.
Constriction vs. Dilation. Constriction and dilation are opposite, but related, processes in the body. Whereas dilation is an opening or widening of a structure or passageway to increase material flow, constriction leads to a decrease in material flow by closing the passage.
Example 7: the dreaded cross-relation. There are four types of motion by which one may progress from one interval to another: parallel, similar, oblique, and contrary. In parallel motion, both voices move in the same direction by the same melodic interval (example 8a). In similar motion, both voices simply move in the same direction (example 8b).